Digitoxigenin alpha-L-arabinoside compounds and therapeutic compositions for combating cardiac insufficiency

ABSTRACT

New digitoxigenin Alpha -L-arabinoside compound of the formula   WHEREIN R1, R2 and R3, which may be the same or different, are acyl (i.e., alkanoyl) or alkyl of up to 3 carbon atoms and one or two of R1, R2 and R3 can also be hydrogen atoms; R1 and R2 together can represent an acetal or ketal grouping containing from 2 to 10 carbon atoms, ARE OUTSTANDINGLY EFFECTIVE IN THE ORAL THERAPY OF CARDIAC INSUFFICIENCY.

United States Patent 1191 Kaiser et al.

[54] DIGITOXIGENIN ALPHA-L-ARABINOSIDE COMPOUNDS AND THERAPEUTICCOMPOSITIONS FOR COMBATING CARDIAC INSUFFICIENCY [75] Inventors: FritzKaiser, Lampertheim; Hans Joachim Lubs, Weinheim; Wolfgang Schaumann,Heidelberg; Wolfgang Voigtl'a'ndel', Viernheim, all of Germany [73Assignee: Boehringer Mannheim GmbH, Mannheim-Waldhof, Germany 22 Filed:Mar. 11, 1974 211 App]. No.: 450,255

[30] Foreign Application Priority Data OTHER PUBLlCATlONS Pigman, TheCarbohydrates, p. 79, Academic Press Inc., New York. 1957.

[451 Oct. 28, 1975 Primary Examiner-Johnnie R. Brown AssistantExaminer-Cary Owens Attorney, Agent, or Firm-Burgess, Dinklage & Sprung[57] ABSTRACT New digitoxigenin a-L-arabinoside compound of the formulawherein R R and R which may be the same or different, are acyl (i.e.,alkanoyl) or alkyl of up to 3 carbon atoms and one or two of R R- and Rcan also be hydrogen atoms; R and R together can represent an acetal orketal grouping containing from 2 to 10 carbon atoms, are outstandinglyeffective in the oral therapy of cardiac insufficiency.

15 Claims, No Drawings NEW DIGITOXIGENIN ALPI-IA-L-ARABINOSIDE COMPOUNDSAND THERAPEUTIC COMPOSITIONS FOR COMBATING CARDIAC INSUFFICIENCY Thepresent invention relates to new digitoxigenin a-L-arabinosidecompounds, with therapeutic compositions containing same, and withtherapeutic methods for combating cardiac insufficiency.

The new inventive compounds are derivatives of digitoxigenina-L-arabinoside of the formula:

wherein R R and R which may be the same or different, are acyl (i.e.,alkanoyl) or alkyl of up to 3 carbon atoms and one or two of R R and Rcan also be hydrogen atoms;

R and R together can represent an acetal or ketal grouping containingfrom 2 to carbon atoms.

Examples of acetal or ketal groupings R R include straight or branchedchain alkylidene, cycloalkylidene and aralkylidene radicals.

Digitoxigenin a-L-arabinoside, which is a cardiac glycoside, is not anaturally-occurring compound but can be prepared partially syntheticallyin good yields. When administered intravenously, it exhibits a goodcardiac effectiveness but, because of its unsatisfactory resorption, itcannot be administered enterally.

We have now found that the new compounds of formula (I) according to thepresent invention possess a high resorption and thus are well suited forthe oral therapy of cardiac insufficiency.

The new compounds (I) according to the present invention can beprepared, for example, by the ketalization or acetalization ofdigitoxigenin a-L-arabinoside and/or by reaction with O-alkylating orO-acylating agents.

The alkylation can be carried out by reaction with appropriatealkylating agents, especially with alkyl halides, dialkyl sulfates ordiazoalkanes. The O-acylation can be carried out with all the acylationagents conventionally used in sugar chemistry, especially with acidanhydrides or orthocarboxylic acid esters or withN,N-dialkylamino-carboxylic acid amide dimethyl acetals and subsequentpartial hydrolysis.

For the preparation of the acetals or ketals, digitoxigenina-L-arabinoside is reacted with an appropriate aldehyde or ketone in thepresence of an appropriate catalyst. As catalyst, there is preferablyused freshly melted zinc chloride, anhydrous copper sulfate, anhydrouscalcium sulfate or an ion exchanger. Instead of aldehydes and ketones,there can be used reactive derivatives thereof, for example thepolymeric and oligo- CH o O o meric aldehydes, as well as the lowerdialkylketals and acetals and the diacyl derivatives.

The following Examples are given for the purpose of illustrating thepresent invention. The hR values given therein were measured on Merckthin layer finished plates Silicagel F 254; impregnation with 20%formamide in acetone; eluent xylenemethyl ethyl ketone (2:3) 5%formamide; detection with trichloroacetic acid-chloramine reagent;fluorescence upon irradiating with ultra-violet light A 366 nm.

EXAMPLE 1 Preparation of Triacetyl-digitoxigenin-a-L-arabinoside l gdigitoxigenin a-L-arabinoside was dissolved in 10 ml pyridine, mixedwith 5 ml acetic anhydride and left to stand for 20 hours at ambienttemperature. Thereafter. the reaction mixture was diluted with water,shaken out with chloroform and the chloroform solution washed with 2Nsulfuric acid and then with water, whereafter it was dried overanhydrous sodium sulfate and evaporated in a vacuum. The crude productthus obtained was dissolved in chloroform, decolorized with charcoal andfiltered over silica gel. The filtrate was evaporated and the residuerecrystallized from etherpetroleum ether. There were obtained 820 mgtriacetyl-digitoxigenin a-Larabinoside; m.p. l l9-l21C; hR value 64.

EXAMPLE 2 Preparation of 4'-Acetyl-digitoxigenin a-L-arabinoside l gdigitoxigenin a-L-arabinoside in 20 ml anhydrous tetrahydrofuran wasmixed with 20 ml orthoacetic acid triethyl ester and 2 g anhydrous zincchloride and stirred for 6 hours at ambient temperature. Subsequently,20 ml water were added to the reaction mixture which was then left tostand for 20 hours at ambient temperature and thereafter poured into 200ml water. After extraction with chloroform, the extract was evaporatedin a vacuum and the residue recrystallized from acetone-ether. Therewere obtained 730 mg 4'- acetyl-digitoxigenin-a-L-arabinoside; m.p.l48-l52C; hR,- value 24.

EXAMPLE 3 Preparation of 3',4-lsopropylidene-digitoxigenina-L-arabinoside l g digitoxigenin a-L-arabinoside, dissolved in 9 mlanhydrous acetone and 9 ml dimethoxypropane, was, after the addition ofl g fAmberlite IR (H* form), stirred for 20 hours at ambienttemperature. Subsequently, the ion exchanger was filtered off and thefiltrate was evaporated in a vacuum. The residue obtained was dissolvedin chloroform and the chloroform solution was filtered over aluminumoxide. The crude product obtained after evaporation of the filtrate wasrecrystallized from chloroform-ether to give 760 mg3',4'-isopropylidene-digitoxigenin a-L-arabinoside; m.p. 184l86C; hRvalue 52.

' EXAMPLE 4 Preparation of 2 '-Acetyl-3 ',4'-isopropylidene-digitoxigenin a-L-arabinoside l g 3',4'-isopropylidene-digitoxigenin a-L- arabinoside, dissolved in 10 mlpyridine, was mixed with 5 ml acetic anhydride and then left to standfor 20 hours at ambient temperature. The reaction mixture was thereafterdiluted with water and shaken out with chloroform.,The chloroform phasewas washed with 2N sulfuric acid and thereafter with water, dried overanhydrous sodium sulfate and evaporated in a vacuum. The residue wasrecrystallized from chloroform-etherpetroleum ether to give 690 mg2-acetyl-3,4- isop ro pylidene-digitoxigenin a-L-arabinoside; m.p.ll8l2lC; hR value 69.

EXAMPLE 5 Preparation of 3,4-Isobutylidene-digitoxigenin a-L-arabinosidel g digitoxigenin a-L-arabinoside, dissolved in ml chloroform-methanol,was mixed with 100 ml methyl ethyl ketone and 10 g anhydrous zincchloride and left to stand for two days at ambient temperature.Thereafter, the reaction mixture was diluted with water, shaken out withchloroform and the chloroform extract evaporated to dryness in a vacuum.For the separation of unreacted digitoxigenin a-L-arabinoside, the crudeproduct was subjected to a multiplicative partitioning with the phasemixture chloroform-carbon tetrachloridemethanol-water (1:l:l:l Theorganic phase was evaporated and the residue was dissolved inchloroform, decolorized with charcoal and filtered over silica gel. Thefiltrate was evaporated and the residue was recrystallized fromacetone-ether. There were obtained 530 mg3,4-isobutylidene-digitoxigenin a-L- arabinoside; m.p. l79l8lC; hR value59.

EXAMPLE 6 Preparation of Cyclohexylidene-digitoxigenin a-L-arabinosideEXAMPLE 7 Preparation of 3,4'-n-Propylidene-digitoxigenina-L-arabinoside l g digitoxigenin a-L-arabinoside, 60 ml propionaldehydeand 400 mg zinc chloride were reacted and worked up in the mannerdescribed in Example 5 to give, after recrystallization of the crudeproduct from acetone-ether, 490 mg 3,4-n-propylidenedigitoxigenina-L-arabinoside; m.p. l53-l56C; hR value 55.

EXAMPLE 8 Preparation of Trimethyl-digitoxigenin a-L-arabinoside l gdigitoxigenin a-L-arabinoside, dissolved in 12 ml dimethyl acetamide,was mixed with 2.8 g barium hydroxide and 3.6 ml dimethyl sulfate andthen stirred for four hours at ambient temperature. Thereafter, thereaction mixture was diluted with 300 ml chloroform, suction filteredover kieselguhr and the kieselguhr then washed with chloroform. 18 mlpyridine were added to the total filtrate, which was then evaporated ina vacisopropylidene-digitoxigenin uum. The residue was dissolved in mlchloroform and shaken out three times with 20 ml amounts of water. Thechloroform phase was then dried over anhydrous sodium sulfate andthereafter filtered and the filtrate evaporated in a vacuum. For theseparation of small amounts of diether, the crude product was subjectedto a multiplicative partitioning with'the phase mixture carbontetrachloride-ethyl acetate-methanol-water (3:1:2z2). After evaporationof the organic phase and recrystallization of the residue fromacetone-ether, there were obtained 860 mg trimethyl-digitoxigenina-L-arabinoside; m.p. 2l4-2l8C; hR value 59.

EXAMPLE 9 Preparation of 3-O-Methyl-digitoxigenin a-L-arabirioside l gdigitoxigenin a-L-arabinoside, dissolved in 13 ml dimethyl formamide and13 ml toluene, was mixed 1.3 g aluminum oxide, 0.16 g barium hydroxideand 0.3 ml dimethyl sulfate in 1.6 ml toluene and then stirred atambient temperature. At intervals of thirty minutes, there were furtheradded ten times 0.16 g barium hydroxide and 0.3 ml dimethyl sulfate in1.6 ml toluene. Thirty minutes after the last addition, the reactionmixture was diluted with 300 ml chloroform, filtered over kieselguhr andthe kieselguhr then washed with chloroform. 18 ml pyridine were added tothe total filtrate, which was then evaporated in a vacuum. The residuewas dissolved in 120 ml chloroform-ethanol (2:1 thereafter shaken outthree times with 20 ml amounts of water, dried over anhydrous sodiumsulfate and the chloroform-ethanol phase then evaporated to dryness. Thecrude product obtained contained, in addition to the desired monomethylether, various dimethyl ethers. For purification, it was dissolved inbenzenechloroform (1:1 and fractionated over 20 g aluminum oxide. Thefractions obtained with 65-70% chloroform gave, after evaporation andrecrystallization from chloroform-ether, 390 mg3'-O-methyl-digitoxigenin a-L- arabinoside; m.p. l86190C; hR value 19.

EXAMPLE 10 Preparation of 2 -O-Methyl-3 ,4 -isopropylidene-digitoxigenina-L-arabinoside l g 3,4'-isopropylidene-digitoxigenin a-L- arabinoside,dissolved in 10 ml dimethyl acetamide, was, after the addition of 2.33 gbarium hydroxide and 3.0 ml dimethyl sulfate, stirred for 2 hours atambient temperature. The reaction mixture was worked up by diluting with120 ml chloroform, filtering over kieselguhr, washing the kieselguhrwith chloroform and adding 18 ml pyridine to the filtrate. The filtratewas then evaporated in a vacuum and the residue was taken up in 120 mlchloroform and washed three times with 20 ml amounts of water. Afterdrying over anhydrous sodium sulfate, the chloroform solution wasevaporated to dryness and the residue dissolved in carbontetrachloride-chloroform (1:1) and then fractionated over 25 g aluminumoxide. The fraction with 50% chloroform gave, averevaporation andrecrystallization of the residue from ether, 720 mg 2-O-methyl-3,4-

a-L-arabinoside; m.p. l3914lC; hR value 74.

As noted above, the instant compounds are useful and efficacious in theoral therapy of cardiac insufficiency. The following experiments wereperformed to illustrate the activity of compounds representative of theinvention in this regard.

The object of the test procedures was to evaluate the resorptionproperties of the compounds of the invention as compared to a knownmaterial, viz., digitoxigenin arabinoside. The criterion of theeffectiveness of the test compounds, when administered enterally, wasthe determination of that period of time, which, following intraduodenalinjection of the compounds to guinea pigs, resulted in ventricularextrasystoles and cardiac arrest.

Test Procedure Guinea pigs which had been subjected to urethaneanesthesia were employed in the tests. A canula was fixedly insertedinto the duodenum above the bile-duct juncture. The test glycosides werethen intraduodenally injected in the dosages as set forth in the tablewhich follows. In each case, ml/kg of an aqueous solution containing 1%methylcellulose and 5% dimethylacetamide was employed as vehicle for thetest compounds. The EKG was followed on the oscilloscope and the exactpoint was determined at which the first ventricular extrasystolesoccurred. If, for a period of 4 seconds no EKG pattern could beobserved, it was established that cardiac arrest had occurred.

On an average, there were six animals used per substance and dose. Theresults are set out in the following table:

TA BLE Guinea pigs lntra- Minutes duodenal, until Active Compound* mg/kgdeath Digitoxigenin-arabinoside 6 l 10 Triacetyl-digitoxigenin- 6 25u-Larabinoside l digitoxigenin-a-L-arabinoside [10] The number inbrackets is the preparative example number, above. in which the compoundwas prepared.

As can be seen from the table, the death of the animals occurs after anappreciably shorter time with the new compounds than withdigitoxigenin-arabinoside, i.e., the invention compounds are resorbedbetter and more quickly than the comparison material.

The new compounds (1) according to the present invention can beadministered enterally and parenterally in solid or liquid form. Forthis purpose, at least one of conventional additives for'injectionsolutions, for example, stabilizing agents, solubilizing agents andbuffers. Additives of this type include, for example, tartrate andcitrate buffers, ethanol, complex-forming agents (such asethylenediamine-tetraacetic acid and the nontoxic salts thereof) andhigh molecular weight polymers (such as liquid polyethylene oxide) forviscosity regulation. Solid carrier materials include, for example,starch, lactose, mannitol, methyl cellulose, talc, highlydispersedsilicic acid, high molecular weight fatty acids (such as stearic acid),gelatine, agar-agar, calcium phosphate, magnesium stearate, animal andvegetable fats and solid high molecular weight polymers (such aspolyethylene glycols). Compositions suitable for oral administrationcan, if desired, contain flavoring and/or sweetening agents.

Usually, the compounds of the invention are administered orally, forinstance in the form of tablets or pills. The new compounds can also beadministerd parenterally, for instance, by intravenous injection. Forthis purpose, they are employed in the form of injectable solutions inwater or isotonic salt solutions.

The compounds according to the present invention are preferably not usedas such in undiluted form but are diluted with suitable diluting agentsas they are conventionally used as pharmaceutical carriers. Suchdilution allows better and more economical use to be made thereof.

For making tablets, pills and other solid forms for medication, uniformdispersion of the active compound throughout the carrier is required.Such a fine and uniform dispersion is achieved, for instance, byintimately mixing and milling the compound according to the presentinvention with a solid pulverulent diluent and, if required, withtableting adjuvants to the desired degree of fineness. One may alsoimpregnate the finely pulverized, solid carrier, while milling, with asolution of the active compound in water or a suitable solvent andremoving the solvent during such milling.

As solid pharmaceutical carriers, various inert pulverulent distributingagents, as they are conventionally used in the pharmaceutical industry,may be employed.

Solid diluents which are admixed to the active compounds, especiallywhen preparing tablets, pills and other compressed forms, are thecommonly used diluting agents, such as cornstarch, dextrose, lactose,sugar and the like. For making tablets and other compressed medicationforms, binders such as pectins, gelatin, gum arabic, methylcellulose,yeast extract, agar, tragacanth, and lubricants such as magnesiumstearate, calcium stearate, stearic acid, talc and the like are used.

The amount of inventive compound present in such preparations may, ofcourse, vary. It is necessary that the active ingredient be containedtherein in such an amount that a suitable dosage will be ensured.Ordinarily, the preparations should not contain less than about 0.1 mgof the inventive compound. The preferred amount in orally administeredpreparations such as tablets, pills and the like, is between about 0.2mg and 1.0 mg per day.

The doses to be administered vary according to the type of actiondesired, i.e., whether said action is to be digitalization ormaintenance. It is, of course, understood that the physician willdetermine the proper amounts to be given to a patient depending upon thesymptons to be alleviated and the patients condition and that the dosesgiven above are by no means limiting the inventive compounds to suchdosages.

It will be understood that the specification and examples areillustrative but not limitative of the present invention and that otherembodiments within the spirit and scope of the invention will suggestthemselves to those skilled in the art.

What is claimed is: v

l. Digitoxigenin a-L-arabinoside compound of the formula wherein R,, Rand R are individually selected from alkanoyl or alkyl of up to 3 carbonatoms and wherein up to two of R,, R and R:, can be hydrogen; or R, andR together can represent an acetal or ketal grouping containing from 2to carbon atoms.

2. Compound as claimedin claim 1, wherein R, is alkanoyl of up to 3carbon atoms.

3. Compound as claimed in claim 1, wherein R is alkanoyl of up to 3carbon atoms.

4. Compound as claimed in claim 1, wherein R is alkanoyl of up to 3carbon atoms.

5. Compound as claimed in claim 1, wherein R, is alkyl of up to 3 carbonatoms.

6. Compound as claimed in claim 1, wherein R is alkyl of up to 3 carbonatoms.

7. Compound as claimed in claim 1, wherein one of R,, R and R ishydrogen.

8. Compound as claimed in claim 1, wherein R, and R taken together,represent an acetal or ketal grouping containing from 2 to 10 carbonatoms.

9. Compound as claimed in claim 8, wherein R, and R representalkylidene.

10. Compound as claimed in claim 8, wherein R, and R representcycloalkylidene.

11. Compound as claimed in claim 8, wherein R, and R representaralkylidene.

12. Compound as claimed in claim 1, designatedtriacetyl-digitoxigenin-a-L-arabinoside.

13. Compound as claimed in claim 1, designated 3',-4'-isopropylidene-digitoxigenin a-L-arabinoside.

14. Compound as claimed in claim 1, designatedtrimethyl-digitoxigenin-oz-L-arabinoside.

15. Compound as claimed in claim 1, designated 2'-O-methyl-3,4'-isopropylidene-digitoxigenin-a-L- arabinoside.

1. DIGITOXIGENIN A-L-ARABINOSIDE COMPOUND OF THE FORMULA
 2. Compound asclaimed in claim 1, wherein R1 is alkanoyl of up to 3 carbon atoms. 3.Compound as claimed in claim 1, wherein R2 is alkanoyl of up to 3 carbonatoms.
 4. Compound as claimed in claim 1, wherein R3 is alkanoyl of upto 3 carbon atoms.
 5. Compound as claimed in claim 1, wherein R2 isalkyl of up to 3 carbon atoms.
 6. Compound as claimed in claim 1,wherein R3 is alkyl of up to 3 carbon atoms.
 7. Compound as claimed inclaim 1, wherein one of R1, R2 and R3 is hydrogen.
 8. Compound asclaimed in claim 1, wherein R1 and R2, taken together, represent anacetal or ketal grouping containing from 2 to 10 carbon atoms. 9.Compound as claimed in claim 8, wherein R1 and R2 represent alkylidene.10. Compound as claimed in claim 8, wherein R1 and R2 representcycloalkylidene.
 11. Compound as claimed in claim 8, wherein R1 and R2represent aralkylidene.
 12. Compound as claimed in claim 1, designatedtriacetyl-digitoxigenin- Alpha -L-arabinoside.
 13. Compound as claimedin claim 1, designated 3'',4''-isopropylidene-digitoxigenin Alpha-L-arabinoside.
 14. Compound as claimed in claim 1, designatedtrimethyl-digitoxigenin- Alpha -L-arabinoside.
 15. Compound as claimedin claim 1, designated 2''-O-methyl-3'',4''-isopropylidene-digitoxigenin- Alpha -L-arabinoside.